It can effect the baby. You have to talk to your doctor about it because if your baby is rh positive then your immune system can attack it. After all your baby recieve nutrients from your blood supply throught the placenta.
Being rh negative shouldn't effect the baby at all. I'm rh negative and the only thing is I have to do it get a shot at 28 weeks. That's what you should be getting also.
The baby moving feels like has bubbles popping. It's a very perticular feeling. At 21 weeks I'm sure you've felt it just don't realize it.